Freight shipping containers are well known, and are available, for example, in lengths such as 20′, 40′, and 48′. Rail cars known as “well” cars have a bottom well which receives either a single long container or two short containers, such as 20′ containers arranged end-to-end.
It is also known to provide on top of two end-to-end 20 foot containers in a well car a 40′ or 48′ foot container stacked on top, which is linked to the two lower level 20′ containers by what are known as semi-automatic inter-box connectors. A number of companies manufacture such semiautomatic inter-box connectors, including Martec, International of South Plainfield, N.J. When such a single long container is provided on top of the two 20′ containers, stability is achieved since the upper container straddles, and is connected to, both of the lower 20′ containers.
For connecting the upper container to the two lower containers, it is known to provide top and bottom corner castings at, or near, the upper and lower four corners of the containers. These castings provide a locking surface containing an oval cutout. The semi-automatic inter-box connectors are arranged between the top and bottom container corner castings and have rotatable locking elements received in the respective oval holes of the top and bottom corner castings, so as to lock the containers together in a vertical configuration.
When two 20′ containers are placed in the well car at the bottom level, although it would be desirable to place a 40′ or 48′ container at the top level, such a container may not be readily available at the loading site. Although it would be desirable to place two additional 20′ containers at a top level and stacked on top of the two lower level 20′ containers, even with the use of the semi-automatic inter-box connectors, lateral stability of the respective stacks would be a major problem which would preclude such an arrangement.